U.S. Pat. No. 4,629,676 (Hayakawa et al.) and European Patent No. 0174634 (Fuji Photo Film Co., Ltd.) disclose an image forming method comprising the steps of imagewise exposing to light a light-sensitive material and heating the light-sensitive material. The light-sensitive material comprises a support and a light-sensitive hardening layer containing silver halide, a reducing agent and a polymerizable compound. The silver halide is developed by heating the light-sensitive material to form a polymer image. The polymerization is initiated by an oxidation radical of the reducing agent (including a radical formed from an oxidation product of the reducing agent).
U.S. Pat. No. 5,122,443 (Takeda), 5,290,659 (Takeda) and European Patent No. 0426192 (Fuji Photo Film Co., Ltd.) disclose embodiments of the light-sensitive materials, which are advantageously used for the preparation of a lithographic plate. In the light-sensitive materials for the lithographic plate, the light-sensitive hardening layer preferably comprises a hardening layer and a light-sensitive layer. The hardening layer contains a polymerizable compound and a hydrophobic polymer. The light-sensitive layer contains silver halide and a hydrophilic polymer. The hardening layer or the light-sensitive layer further contains a reducing agent. The light-sensitive material can further comprise an image formation accelerating layer containing a base or base precursor provided on the light-sensitive layer.
A process for the preparation of a lithographic plate comprises the steps of imagewise exposing to light the light-sensitive material, heating the material, removing the light-sensitive layer from the material and removing the unhardened area of the hardening layer with an alkaline etching solution. The formed replica image is used as a printing plate. The hydrophobic polymer in the hardening layer preferably has an acidic group, which has a function of dissolving the polymer in the etching solution.
The hardening layer containing a polymerizable compound and a hydrophobic polymer is hydrophobic, while the light-sensitive layer containing silver halide and a hydrophilic polymer is hydrophilic. Accordingly, the adhesion between the two layers is weak. The light-sensitive material was sometimes destroyed by separation between the layers while handling the light-sensitive material. The separation was caused when a pressure is applied to the light-sensitive material, for example when the material was cut, the surface of the material was rubbed, the material was rolled or stacked, or the material was taken out from a roll or a stack.
Japanese Patent Provisional Publication Nos. 8(1996)-123035, 8(1996)-146600, 8(1996)-184968 and 8(1996)-194314 disclose silver halide light-sensitive materials improved in the adhesion between the hardening layer and the light-sensitive layer.
Japanese Patent Provisional Publication No. 8(1996)-123035 discloses a light-sensitive material containing a hydrophobic polymer having an acidic group in the form of a salt as a binder of a hardening layer. Japanese Patent Provisional Publication No. 8(1996)-146600 discloses a process for the preparation of a light-sensitive material in which a coating solution for a hardening layer contains a hydrophobic polymer in a mixture of a good solvent and a poor solvent. The boiling point of the poor solvent is higher than that of the good solvent, and the difference between the boiling points is not less than 3.degree. C. Japanese Patent Provisional Publication No. 8(1996)-184968 discloses a light-sensitive material comprising a hardening layer containing a hydrophilic polymer having an acidic group and a light-sensitive layer containing a hydrophilic polymer and an aminoalcohol. Japanese Patent Provisional Publication No. 8(1996)-194314 discloses a light-sensitive material comprising an adhesive layer provided between a hardening layer and a light-sensitive layer. The adhesive layer contains a polymer or an additive proposed in the above-mentioned publications.
The above-mentioned publications propose modifying a polymer that has been used as a binder of a hardening layer or a light-sensitive layer to enhance the adhesion between the layers. It has been proved that the binder of the hardening layer or the light-sensitive layer has no adverse effects on the light-sensitive material or the image forming system.